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Add comment; refactor; avoid pulling in DT if it's not used.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93306 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2010-01-13 07:59:13 +00:00
parent ee9250bb4f
commit d89d5180d1
1 changed files with 114 additions and 83 deletions
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197
lib/CodeGen/OptimizeExts.cpp
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@ -6,6 +6,16 @@
// License. See LICENSE.TXT for details. // License. See LICENSE.TXT for details.
// //
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
//
// This pass performs optimization of sign / zero extension instructions. It
// may be extended to handle other instructions of similar property.
//
// On some targets, some instructions, e.g. X86 sign / zero extension, may
// leave the source value in the lower part of the result. This pass will
// replace (some) uses of the pre-extension value with uses of the sub-register
// of the results.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "ext-opt" #define DEBUG_TYPE "ext-opt"
#include "llvm/CodeGen/Passes.h" #include "llvm/CodeGen/Passes.h"
@ -40,9 +50,15 @@ namespace {
virtual void getAnalysisUsage(AnalysisUsage &AU) const { virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG(); AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU); MachineFunctionPass::getAnalysisUsage(AU);
AU.addRequired<MachineDominatorTree>(); if (Aggressive) {
AU.addPreserved<MachineDominatorTree>(); AU.addRequired<MachineDominatorTree>();
AU.addPreserved<MachineDominatorTree>();
}
} }
private:
bool OptimizeInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs);
}; };
} }
@ -52,98 +68,113 @@ X("opt-exts", "Optimize sign / zero extensions");
FunctionPass *llvm::createOptimizeExtsPass() { return new OptimizeExts(); } FunctionPass *llvm::createOptimizeExtsPass() { return new OptimizeExts(); }
bool OptimizeExts::runOnMachineFunction(MachineFunction &MF) { /// OptimizeInstr - If instruction is a copy-like instruction, i.e. it reads
TM = &MF.getTarget(); /// a single register and writes a single register and it does not modify
TII = TM->getInstrInfo(); /// the source, and if the source value is preserved as a sub-register of
MRI = &MF.getRegInfo(); /// the result, then replace all reachable uses of the source with the subreg
DT = &getAnalysis<MachineDominatorTree>(); /// of the result.
bool OptimizeExts::OptimizeInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs) {
bool Changed = false; bool Changed = false;
LocalMIs.insert(MI);
SmallPtrSet<MachineInstr*, 8> LocalMIs; unsigned SrcReg, DstReg, SubIdx;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) { if (TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx)) {
MachineBasicBlock *MBB = &*I; if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
for (MachineBasicBlock::iterator MII = I->begin(), ME = I->end(); MII != ME; TargetRegisterInfo::isPhysicalRegister(SrcReg))
++MII) { return false;
MachineInstr *MI = &*MII;
LocalMIs.insert(MI);
unsigned SrcReg, DstReg, SubIdx; MachineRegisterInfo::use_iterator UI = MRI->use_begin(SrcReg);
if (TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx)) { if (++UI == MRI->use_end())
if (TargetRegisterInfo::isPhysicalRegister(DstReg) || // No other uses.
TargetRegisterInfo::isPhysicalRegister(SrcReg)) return false;
continue;
MachineRegisterInfo::use_iterator UI = MRI->use_begin(SrcReg); // Ok, the source has other uses. See if we can replace the other uses
if (++UI == MRI->use_end()) // with use of the result of the extension.
// No other uses. SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs;
continue; UI = MRI->use_begin(DstReg);
for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
++UI)
ReachedBBs.insert(UI->getParent());
// Ok, the source has other uses. See if we can replace the other uses bool ExtendLife = true;
// with use of the result of the extension. // Uses that are in the same BB of uses of the result of the instruction.
SmallVector<MachineOperand*, 8> Uses;
// Uses that the result of the instruction can reach.
SmallVector<MachineOperand*, 8> ExtendedUses;
SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs; UI = MRI->use_begin(SrcReg);
UI = MRI->use_begin(DstReg); for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE; ++UI) {
++UI) MachineOperand &UseMO = UI.getOperand();
ReachedBBs.insert(UI->getParent()); MachineInstr *UseMI = &*UI;
if (UseMI == MI)
continue;
MachineBasicBlock *UseMBB = UseMI->getParent();
if (UseMBB == MBB) {
// Local uses that come after the extension.
if (!LocalMIs.count(UseMI))
Uses.push_back(&UseMO);
} else if (ReachedBBs.count(UseMBB))
// Non-local uses where the result of extension is used. Always
// replace these.
Uses.push_back(&UseMO);
else if (Aggressive && DT->dominates(MBB, UseMBB))
// We may want to extend live range of the extension result in order
// to replace these uses.
ExtendedUses.push_back(&UseMO);
else {
// Both will be live out of the def MBB anyway. Don't extend live
// range of the extension result.
ExtendLife = false;
break;
}
}
bool ExtendLife = true; if (ExtendLife && !ExtendedUses.empty())
SmallVector<MachineOperand*, 8> Uses; // Ok, we'll extend the liveness of the extension result.
SmallVector<MachineOperand*, 8> ExtendedUses; std::copy(ExtendedUses.begin(), ExtendedUses.end(),
std::back_inserter(Uses));
UI = MRI->use_begin(SrcReg); // Now replace all uses.
for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE; if (!Uses.empty()) {
++UI) { const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
MachineOperand &UseMO = UI.getOperand(); for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
MachineInstr *UseMI = &*UI; MachineOperand *UseMO = Uses[i];
if (UseMI == MI) MachineInstr *UseMI = UseMO->getParent();
continue; MachineBasicBlock *UseMBB = UseMI->getParent();
MachineBasicBlock *UseMBB = UseMI->getParent(); unsigned NewVR = MRI->createVirtualRegister(RC);
if (UseMBB == MBB) { BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
// Local uses that come after the extension. TII->get(TargetInstrInfo::EXTRACT_SUBREG), NewVR)
if (!LocalMIs.count(UseMI)) .addReg(DstReg).addImm(SubIdx);
Uses.push_back(&UseMO); UseMO->setReg(NewVR);
} else if (ReachedBBs.count(UseMBB)) ++NumReuse;
// Non-local uses where the result of extension is used. Always Changed = true;
// replace these.
Uses.push_back(&UseMO);
else if (Aggressive && DT->dominates(MBB, UseMBB))
// We may want to extend live range of the extension result in order
// to replace these uses.
ExtendedUses.push_back(&UseMO);
else {
// Both will be live out of the def MBB anyway. Don't extend live
// range of the extension result.
ExtendLife = false;
break;
}
}
if (ExtendLife && !ExtendedUses.empty())
// Ok, we'll extend the liveness of the extension result.
std::copy(ExtendedUses.begin(), ExtendedUses.end(),
std::back_inserter(Uses));
// Now replace all uses.
if (!Uses.empty()) {
const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
MachineOperand *UseMO = Uses[i];
MachineInstr *UseMI = UseMO->getParent();
MachineBasicBlock *UseMBB = UseMI->getParent();
unsigned NewVR = MRI->createVirtualRegister(RC);
BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
TII->get(TargetInstrInfo::EXTRACT_SUBREG), NewVR)
.addReg(DstReg).addImm(SubIdx);
UseMO->setReg(NewVR);
++NumReuse;
Changed = true;
}
}
} }
} }
} }
return Changed; return Changed;
} }
bool OptimizeExts::runOnMachineFunction(MachineFunction &MF) {
TM = &MF.getTarget();
TII = TM->getInstrInfo();
MRI = &MF.getRegInfo();
DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : 0;
bool Changed = false;
SmallPtrSet<MachineInstr*, 8> LocalMIs;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = &*I;
LocalMIs.clear();
for (MachineBasicBlock::iterator MII = I->begin(), ME = I->end(); MII != ME;
++MII) {
MachineInstr *MI = &*MII;
Changed |= OptimizeInstr(MI, MBB, LocalMIs);
}
}
return Changed;
}